The present invention relates to the field of power over Ethernet and more particularly to a dual mode power over Ethernet controller.
The growth of local and wide area networks based on Ethernet technology has been an important driver for cabling offices and homes with structured cabling systems having multiple twisted wire pairs. The ubiquitous local area network, and the equipment which operates thereon, has led to a situation where there is often a need to attach a network operated device for which power is to be advantageously supplied by the network over the network wiring. Supplying power over the network wiring has many advantages including, but not limited to; reduced cost of installation; centralized power and power back-up; and centralized security and management.
Several patents addressed to this issue exist including: U.S. Pat. No. 6,473,608 issued to Lehr et al., whose contents are incorporated herein by reference and U.S. Pat. No. 6,643,566 issued to Lehr et al., whose contents are incorporated herein by reference. Furthermore a standard addressed to the issue of powering remote devices over an Ethernet based network has been published as IEEE 802.3af-2003, whose contents are incorporated herein by reference.
An Ethernet switch is typically designed to support a plurality of ports, and power over Ethernet functionality may be supplied for some or all of the supported plurality of ports. For example, in a 48 port Ethernet switch or hub, only 12 or alternatively 24 of the ports may be initially supplied with power over Ethernet functionality. A separate module is later added to supply power over Ethernet functionality to additional ports. Power over Ethernet functionality is typically provided by a power over Ethernet controller, also termed herein power over Ethernet managing circuitry.
In such a configuration, the initially supplied power over Ethernet controller must supply 100% of the required functionality for the initial ports for which Power over Ethernet functionality is being provided, including any required supervisory control circuitry. The later added module may be provided without supervisory control circuitry, receiving its instructions from the supervisory control circuitry of the initially provided module. Preferably, different module types are available, with an enhanced module having added functionality not available in the basic module.
The term supervisory control circuitry is meant to include any circuitry which is capable of providing supervisory control functionality for a plurality of power over Ethernet managing circuits. Such supervisory control circuitry may be included as part of one or more power over Ethernet managing circuits, or as a separate controller or microcontroller.
What is needed, and not supplied by the prior art, is a single power over Ethernet controller having a plurality of operating modes, enabling the single power over Ethernet controller to function in cooperation with basic supervisory control circuitry and enhanced supervisory control circuitry having added functionality.